The present invention relates to a roof load carrier for vehicles having two roof rails which are fixed on the surface of the roof and extend generally parallel to each other along the side edges of the surface of the roof. Each roof rail has an upper support surface and an elongated inner channel which opens toward the outside of the rail. The channel opening is formed by inwardly directed flanges in an engagement wall of the roof rails. There is a front and a rear transverse bar which are mounted adjustably on the roof rails. Each of the bars is supported on and displaceable along the supporting surface of the roof rails via support feet. Fastening devices fasten the support feet to the roof rails. Each of those devices comprises a clamping plate arranged within the channel and a headed bolt having a threaded shank, which extends through the channel opening and is in threaded engagement with the clamping plate.
In a known roof load carrier of this type, a force locked attachment is provided between the roof rails and the transverse bars. That attachment is produced in each case via the headed bolt and the clamping plate. If the vehicle is subjected to strong acceleration or deceleration, as may occur, for instance, in a collision with another vehicle or with an obstacle or else due to sudden braking, high forces act on the roof load carrier and on the transported articles fastened to it as a result of the moment of inertia. The clamp attachment does not always withstand this stress. In the extreme case, the roof load carrier may be torn off the roof of the vehicle, and the transverse carriers together with the articles being transported first sliding in the longitudinal direction of the rails.